Field of the Invention
The present invention relates to extended discontinuous reception (DRX) signaling for connected mode user equipments (UEs).
Related Background Art
The following meanings for the abbreviations used in this specification apply:
C-RNTI Cell Radio Network Temporary Identifier
DRX Discontinuous Reception
LTE Long Term Evolution
PDCCH Physical Downlink Control Channel
RAN Radio Access Network
RRC Radio Resource Control
SIB System Information Block
UE User Equipment
For UE energy saving purpose, DRX has been defined in LTE. If an UE is configured with DRX by higher layer, the UE is not required to monitor PDCCH when it is not in active time as show in FIG. 1. FIG. 1 illustrates a DRX cycle in which the UE monitors PDCCH during “On Duration” (active time), and does not monitor PDCCH during “Opportunity for DRX”.
DRX is configured by RRC with the following parameters:
DRX-Config ::=CHOICE {releaseNULL,setupSEQUENCE {onDurationTimerENUMERATED {psf1,psf2, psf3, psf4, psf5, psf6,psf8, psf10, psf20, psf30, psf40,psf50, psf60, psf80, psf100,psf200},drx-InactivityTimerENUMERATED {psf1, psf2, psf3, psf4, psf5, psf6,psf8, psf10, psf20, psf30, psf40,psf50, psf60, psf80, psf100,psf200, psf300, psf500, psf750,psf1280, psf1920, psf2560,spare10, spare9, spare8, spare7,spare6, spare5, spare4, spare3,spare2, spare1},drx-RetransmissionTimerENUMERATED {psf1, psf2, psf4, psf6, psf8, psf16,psf24, psf33},longDRX-CycleStartOffsetCHOICE {sf10INTEGER(0..9),sf20INTEGER(0..19),sf32INTEGER(0..31),sf40INTEGER(0..39),sf64INTEGER(0..63),sf80INTEGER(0..79),sf128INTEGER(0..127),sf160INTEGER(0..159),sf256INTEGER(0..255),sf320INTEGER(0..319),sf512INTEGER(0..511),sf640INTEGER(0..639),sf1024INTEGER(0..1023),sf1280INTEGER(0..1279),sf2048INTEGER(0..2047),sf2560INTEGER(0..2559)},shortDRXSEQUENCE {shortDRX-CycleENUMERATED{sf2, sf5, sf8, sf10, sf16, sf20,sf32, sf40, sf64, sf80, sf128, sf160,sf256, sf320, sf512, sf640},drxShortCycleTimerINTEGER (1..16)}OPTIONAL-- Need OR}}-- ASN1STOP
The above parameter “longDRX-CycleStartOffset” comprises longDRX-Cycle and drxStartOffset. The value of longDRX-Cycle is in number of sub-frames. Value sf10 corresponds to 10 sub-frames, sf20 corresponds to 20 sub-frames and so on. If shortDRX-Cycle is configured, the value of longDRX-Cycle should be a multiple of the shortDRX-Cycle value. The value of drxStartOffset value is in number of sub-frames.
The above parameter “onDurationTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.
The above parameter “drx-InactivityTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.
The above parameter “drx-RetransmissionTimer” is a timer for DRX. Its value is in number of PDCCH sub-frames. Value psf1 corresponds to 1 PDCCH sub-frame, psf2 corresponds to 2 PDCCH sub-frames and so on.
The value of the above parameter “shortDRX-Cycle” is in number of sub-frames. Value sf2 corresponds to 2 sub-frames, sf5 corresponds to 5 subframes and so on.
The above parameter “drxShortCycleTimer” is a timer for DRX. Its value is in multiples of shortDRX-Cycle. A value of 1 corresponds to shortDRX-Cycle, a value of 2 corresponds to 2*shortDRX-Cycle and so on.
For power saving purposes, RAN is considering extending connected mode DRX way beyond the current maximum of 2560 ms, e.g. to one hour.
For example, in order to support a DRX cycle of one hour (3600 s or 3,600,000 ms), a straightforward extension of the current signaling would be to introduce as long DRX-CycleStartOffset parameter the following:
sf3600000INTEGER(0..3599999)
Clearly, when introducing very large DRX cycles (or extended DRX), a 1 ms granularity is not needed to spread the UEs: the number of ms within a cycle is largely superior to the number of UEs that can be supported. For instance, only 65,536 C-RNTI can be allocated (16 bits long), which is to be compared to the 3,600,000 possible offsets in the example of the 1 hour DRX cycle above: ˜100 times more offsets than required.